1. Field of the Invention
The present invention relates to an optical disc read apparatus and method, and more particularly to an optical disc read apparatus and method in which different light beams are applied at the same time to a plurality of adjacent tracks of an optical disc formed with a spiral track, such CD-ROM, CD-WO, DVD, DVD-ROM, and DVD-RAM, and data recorded on the tracks applied with the light beams are read with a record data read system in accordance with a detected output of each reflected light beam.
2. Description of the Related Art
A multibeam method is one of the methods of reading record data from a CD-ROM at high speed. With this method, different light beams are applied at the same time to a plurality of adjacent tracks of an optical disc formed with a spiral track, data recorded on the tracks applied with the light beams are read with a record data read system in accordance with a detected output of each reflected light beam, and the read data are sequentially output in the record order by preventing the read data from being duplicated or omitted.
A multibeam method of reading an optical disc (CD-ROM) will be described with reference to FIG. 21. Reference numeral 1 represents an optical disc (CD-ROM) as viewed toward a signal plane (from an optical pickup side), CD-ROM being formed with a spiral track recorded with data (the outer and inner circumference sides of CD-ROM are indicated by arrows in FIG. 21). Reference numeral 2 represents an optical pickup capable of radiating five light beams, the optical pickup 2 being provided with a relative rotation to CD-ROM 1 and moved from the inner circumference to outer circumference as record data read advances. As the optical pickup 2 reaches a position I and starts reading record data, light beams 31 to 35 are applied at the same time to respective tracks (xxe2x88x921) to (x+3) and data recorded on the tracks applied with the light beams 31 to 35 are read with a record data read system in accordance with a detected output of each reflected light beam.
Record data of CD-ROM 1 is formed on the basis of one frame unit (one frame=1/75 sec) represented by A-time (Absolute-time) of a sub-code Q channel, in conformity with the CD signal format. As the optical pickup 2 starts reading data from the position I shown in FIG. 21, the optical beam 31 system correctly reads record data from the frame of A-time=23:40:59 or 23 minutes, 40 seconds, 59 frames, the optical beam 32 system correctly reads record data from the frame of A-time=23:40:74, the optical beam 33 system correctly reads record data from the frame of A-time=23:41:14, the optical beam 34 system correctly reads record data from the frame of A-time=23:41:29, and the optical beam 35 system correctly reads record data from the frame of A-time=23:41:44.
As CD-ROM 1 rotates generally once (slightly more than once) and the read position with the optical pickup 2 reaches a position II shown in FIG. 21 (the light beams 31 to 35 are applied to the tracks x to (x+4), the optical beam 31 correctly reads record data up to the frame of A-time=23:40:73, the optical beam 32 correctly reads record data up to the frame of A-time=23:41:13, the optical beam 33 correctly reads record data up to the frame of A-time=23:41:28, and the optical beam 34 correctly reads record data up to the frame of A-time=23:41:43. In this manner, there is no omission of read data by the optical beams 31 to 35 (at this time, the light beam 35 has correctly read record data up to the frame of A-time=23:41:58). The data read by the optical beams 31 to 35 are output to external circuits in the record order by preventing the read data from being duplicated.
When the read position with the optical pickup 2 reaches the position II shown in FIG. 21, the optical pickup 2 is jumped forward (toward the outer circumference of CD-ROM 1) by three tracks. Namely, the optical pickup 2 is jumped to a position III shown in FIG. 21 (and the light beams 31 to 35 are applied to tracks (x+3) to (x+7)). Thereafter, data read starts again. Specifically, the optical beam 31 system correctly reads record data from the frame of A-time=23:41:46, the optical beam 32 system correctly reads record data from the frame of A-time=23:41:61, the optical beam 33 system correctly reads record data from the frame of A-time=23:42:01, the optical beam 34 system correctly reads record data from the frame of A-time=23:42:16, and the optical beam 35 system correctly reads record data from the frame of A-time=23:42:31.
As CD-ROM 1 rotates generally once (slightly more than once) and the read position with the optical pickup 2 reaches a position IV shown in FIG. 21 (the light beams 31 to 35 are applied to the tracks (x+4) to (x+8), the optical beam 31 system correctly reads record data up to the frame of A-time=23:41:60, the optical beam 32 system correctly reads record data up to the frame of A-time=23:42:00, the optical beam 33 system correctly reads record data up to the frame of A-time=23:42:15, and the optical beam 34 system correctly reads record data up to the frame of A-time=23:42:30. In this manner, there is no omission of read data by the optical beams 31 to 35 (at this time, the light beam 35 has correctly read record data up to the frame of A-time=23:42:45). The data read by the optical beams 31 to 35 are output to the external circuits in the record order by preventing the read data from being duplicated.
When the read position with the optical pickup 2 reaches the position IV shown in FIG. 21, the optical pickup 2 is jumped forward (toward the outer circumference of CD-ROM 1) by three tracks. Namely, the optical pickup 2 is jumped to a position V shown in FIG. 21 (and the light beams 31 to 35 are applied to tracks (x+7) to (3+11)). Thereafter, data read starts again. Specifically, the optical beam 31 system correctly reads record data from the frame of A-time=23:42:33, the optical beam 32 system correctly reads record data from the frame of A-time=23:42:48, the optical beam 33 system correctly reads record data from the frame of A-time=23:42:63, the optical beam 34 system correctly reads record data from the frame of A-time=23:43:03, and the optical beam 35 system correctly reads record data from the frame of A-time=23:43:18.
As CD-ROM 1 rotates generally once (slightly more than once) and the read position with the optical pickup 2 reaches a position VI shown in FIG. 21 (the light beams 31 to 35 are applied to the tracks (x+8) to (x+12), the optical beam 31 system correctly reads record data up to the frame of A-time=23:42:47, the optical beam 32 system correctly reads record data up to the frame of A-time=23:42:62, the optical beam 33 system correctly reads record data up to the frame of A-time=23:43:02, and the optical beam 34 system correctly reads record data up to the frame of A-time=23:43:17. In this manner, there is no omission of read data by the optical beams 31 to 35 (at this time, the light beam 35 has correctly read record data up to the frame of A-time=23:43:32). The data read by the optical beams 31 to 35 are output to the external circuits in the record order by preventing the read data from being duplicated.
When the read position with the optical pickup 2 reaches the position VI shown in FIG. 21, the optical pickup 2 is jumped forward (toward the outer circumference of CD-ROM 1) by three tracks. Namely, the optical pickup 2 is jumped to a position VII shown in FIG. 21 (and the light beams 31 to 35 are applied to tracks (3+11) to (x+15)). Thereafter, data read starts again. Specifically, the optical beam 31 system correctly reads record data from the frame of A-time=23:43:20, the optical beam 32 system correctly reads record data from the frame of A-time=23:43:35, the optical beam 33 system correctly reads record data from the frame of A-time=23:43:50, the optical beam 34 system correctly reads record data from the frame of A-time=23:43:65, and the optical beam 35 system correctly reads record data from the frame of A-time=23:44:05.
As CD-ROM 1 rotates generally once (slightly more than once) and the read position with the optical pickup 2 reaches a position VIII shown in FIG. 21 (the light beams 31 to 35 are applied to the tracks (x+12) to (x+16), the optical beam 31 system correctly reads record data up to the frame of A-time=23:43:34, the optical beam 32 system correctly reads record data up to the frame of A-time=23:43:49, the optical beam 33 system correctly reads record data up to the frame of A-time=23:43:64, and the optical beam 34 system correctly reads record data up to the frame of A-time=23:44:04. In this manner, there is no omission of read data by the optical beams 31 to 35 (at this time, the light beam 35 has correctly read record data up to the frame of A-time=23:44:19). The data read by the optical beams 31 to 35 are output to the external circuits in the record order by preventing the read data from being duplicated.
While the optical pickup 2 is given a relative rotation to CD-ROM 1 from the position I to the position II, the light beam 35 system reads the record data from the frame of A-time=23:41:44 to the frame of A-time=23:41:58, whereas while the optical pickup 2 is given a relative rotation to CD-ROM 1 from the position III to the position IV, the light beam 31 system reads the record data from the frame of A-time=23:41:46 to the frame of A-time=23:41:60. Therefore, record data from the frame of A-time=23:41:46 to the frame of A-time=23:41:58 is duplicated. Therefore, for the record data from the frame of A-time=23:41:46 to the frame of A-time=23:41:58, the record data previously read with the light beam 35 is output and the record data read with the light beam 31 is discarded.
When the track jump is performed from the position II shown in FIG. 21, the optical pickup 2 is jumped not by four tracks, but by three tracks in order to apply the light beam 31 to the track (x+3) from which the record data was read with the light beam 35 system immediately before the track jump. If the number of jump tracks is xe2x80x9c4xe2x80x9d, the optical pickup 2 is jumped to a position IIIxe2x80x2 shown in FIG. 21, and thereafter the light beam 31 system reads record data from the frame of A-time=23:41:61. Therefore, the record data in the frames of A-time=23:41:59 and A-time=23:41:61 still not read with the light beam 35 before the track jump are omitted.
Generally, high speed read of CD-ROM 1 is performed by repeating an operation of reading record data with n (n is an integer xe2x80x9c3xe2x80x9d or larger) light beam systems for one rotation and then making the optical pickup jump forward by (nxe2x88x922) tracks.
When a track jump is performed, the focus servo system and tracking servo system are temporarily disturbed so that record data read cannot resume until these servo systems become stable.
With the conventional multibeam optical disc read method described above, if the number n of light beams is xe2x80x9c5xe2x80x9d, it is necessary to perform a continuous read by about four rotations of CD-ROM 1 and three track jumps in order to read record data from the tracks (xxe2x88x921) to (x+16) shown in FIG. 21. Since a fairly long time is necessary for each track jump, it takes a long time to read data recorded in a number of tracks.
Record data read with some light beam systems may become impossible because of a track pitch variation, surface vibration, center deviation and the like of CD-ROM 1. In such a case, the conventional optical disc read method of repeating an operation of reading record data with n (n is an integer xe2x80x9c3xe2x80x9d or larger) light beam systems for approximately one rotation and then making the optical pickup jump forward by (nxe2x88x922) tracks, is associated with some problem. For example, if the light beam 32 system shown in FIG. 21 is unable to read record data, the record data in the frames from A-time=23:40:74 to A-time=23:41:13 cannot be read during the record data read with the optical pickup 2 by approximately one rotation from the position I shown in FIG. 21.
As the optical pickup 2 reaches the position II, the track jump by three tracks to the position III is performed. Therefore, the record data in the frames from A-time=23:40:74 to A-time=23:41:13 cannot be read. Also, the record data in the frames from A-time=23:41:61 to A-time=23:42:00 cannot be read during the record data read by approximately one rotation from the position III.
As above, a problem occurs that a user cannot acquire a portion of necessary data.
It is an object of the present invention to solve the above problem and provide an optical disc read method and apparatus capable of reading data at high speed from an optical disc.
It is another object of the present invention to provide an optical disc read method and apparatus capable of acquiring necessary data even if data read with some light beams is impossible.
It is a further object of the present invention to provide an optical disc read method and apparatus capable of efficiently reading record data from an optical disc even if data read with some light beams is impossible.
In an optical disc read method according to the invention, data recorded on tracks of an optical disc formed with a spiral track is read with a record data read system by applying different light beams 1, . . . , n at the same time to n tracks at every (c+1)-th and independently detecting the light beams reflected from the optical disc, where c is an integer of 1 or larger and n is an integer of 2 or larger, and the record data of the optical disc is read by alternately performing an operation of continuously reading the record data on the tracks of the optical disc with n light beam systems and a track jump operation in a forward direction after the continuous reading operation.
The continuous reading operation may be performed during approximately (c+1) rotations of the optical disc, and the track jump operation jumps approximately {(c+1) (nxe2x88x921)xe2x88x921} tracks in the forward direction.
If there is a light beam system unable to read the record data of the optical disc, among the n light beam systems, the record data of the optical disc may be read by alternately performing an operation of continuously reading the record data on the tracks of the optical disc with n light beam systems during approximately (c+1) rotations and a track jump operation by approximately {(c+1)xc2x7(Mxe2x88x921)xe2x88x921} tracks in a forward direction after the continuous reading operation, by using detection outputs from only M (M less than n) adjacent record data readable light beam systems.
M is the maximum number of adjacent record data readable light beam systems among record data readable light beam systems.
Alternatively, if there is a light beam system unable to read the record data of the optical disc, among the n light beam systems and if Q is 2 or larger and R is 0 or larger, where Q is the number of tracks representing a distance between the innermost light beam and outermost light beam among record data readable light beam systems and R is the maximum number of adjacent record data unreadable light beams between the innermost and outermost record data readable light beams, the record data of the optical disc may be read by alternately performing an operation of continuously reading the record data on the tracks of the optical disc with the record data readable light beam systems during approximately {(R+1)xc2x7(c+1)} and a track jump operation by approximately (Qxe2x88x921) tracks in a forward direction after the continuous reading operation with a combination of the record data readable light beam systems shows no omission of the record data of the optical disc.
The record data detected from the tracks of the optical disc during the continuous reading operation may be stored together with frame addresses, and the track jump operation may be performed when a frame address corresponding to the record data read with the i-th light beam becomes continuous with a continuous data read start frame address corresponding to the record data to be read with the adjacent (i+1)-th light beam.
According to another aspect of the optical disc read method of this invention, data recorded on tracks of an optical disc formed with a spiral track is read with a record data read system by applying different light beams at the same time to n tracks at every (c+1)-th and independently detecting the light beams reflected from the optical disc, where c is an integer of 1 or larger and n is an integer of 2 or larger; a system capable of reading the record data from the optical disc is detected from n light beam systems by applying the light beams to predetermined positions of the tracks of the optical disc at a start of a continuous data reading operation and continuously reading the record data; and each light beam is set so that one of the detected record data readable systems is applied to a read start track frame.
After each light beam is set so that one of the detected record data readable systems is applied to a read start track frame, the record data of the optical disc may be read by alternately performing an operation of continuously reading the record data during a predetermined number of rotations of the optical disc and a track jump operation by a predetermined number of tracks, the rotation number and the track number being determined in accordance with the number and layout of the record data readable systems.
The predetermined positions of the tracks of the optical disc may be positions more in a backward direction than the read start track frame.
In an optical disc read apparatus embodying the optical disc read method, record data reading means includes a memory for storing the record data obtained during the continuous reading operation and a corresponding frame address, and read control means performs the track jump operation when a frame address corresponding to the record data read with the i-th light beam becomes continuous with a continuous data read start frame address corresponding to the record data to be read with the adjacent (i+1)-th light beam.
According to the invention, since the continuous read of an optical disc is performed approximately during (c+1) rotations, the number of track jumps which take a long process time can be reduced so that record data of the optical disc in a desired area can be read quickly.
Even if the record data cannot be read with some light beam systems because of a track pitch variation, surface vibration, center deviation and the like of an optical disc, desired data of the optical disc can be read reliably and quickly with some or all the remaining record data readable light beam systems by preventing the record data from being omitted.